Azithromycin Safety at 25 Weeks Gestation
Yes, azithromycin is safe to use at 25 weeks of pregnancy and is classified as FDA Pregnancy Category B, with CDC guidelines recommending it as a preferred macrolide antibiotic during pregnancy. 1, 2, 3
FDA Classification and Safety Profile
Azithromycin is designated as FDA Pregnancy Category B, meaning animal reproduction studies have shown no evidence of harm to the fetus at doses up to 4 times (rats) and 2 times (mice) the human daily dose of 500 mg, though adequate and well-controlled studies in pregnant women are lacking. 3
The CDC specifically identifies azithromycin as the preferred macrolide antibiotic during pregnancy based on animal studies and clinical experience showing its safety profile. 2
No conclusive evidence exists that azithromycin use during pregnancy causes adverse fetal outcomes, according to CDC guidelines. 2
Clinical Evidence Supporting Safety
A prospective cohort study of 123 pregnant women exposed to azithromycin (71.6% during first trimester) found no statistically significant increase in major malformations compared to disease-matched controls (3.4% vs 2.3%) or non-teratogen controls (3.4%), which is within the baseline rate of 1-3%. 4
Pharmacokinetic studies in pregnant women at various gestational ages demonstrate that azithromycin is well-tolerated, with pregnancy causing an 86% increase in volume of distribution but no significant change in drug exposure (AUC), and no dose adjustment is needed. 5
Animal studies in sheep at 80 days gestation (equivalent to second trimester) showed substantial fetal tissue uptake with repeated maternal intravenous dosing, with no evidence of fetal injury, hepatotoxicity, or inflammatory markers. 6
Approved Indications During Pregnancy
Chlamydial infections: CDC recommends azithromycin 1g orally as a single dose as first-line treatment during pregnancy due to superior efficacy, safety profile, and excellent compliance. 7
MAC prophylaxis in HIV-infected pregnant women: Azithromycin is specifically recommended as the drug of choice. 2
Pertussis treatment and prophylaxis: Azithromycin is the preferred macrolide, particularly for infants <1 month and by extension for pregnant women. 1
Important Clinical Caveats
Do not confuse with clarithromycin, which has been demonstrated to be a teratogen in animals and should be used with caution during pregnancy. 2
While a 2022 review noted conflicting results regarding risks of spontaneous miscarriage, congenital malformations, and preterm birth in some studies, the authors concluded there is no conclusive evidence supporting that azithromycin causes adverse offspring outcomes. 8
Azithromycin should only be used when clinically indicated during pregnancy, ensuring benefits outweigh potential risks. 3, 8
The drug is excreted in breast milk, so caution should be exercised if breastfeeding, though this is not relevant at 25 weeks gestation. 3